The Leo Triplet of Galaxies

     There has not been a great sky for galaxies here since April 5th.  However, the upcoming early week forecast looks good.  There have been a few nights with lots of haze, including the last few nights.  Thursday was the full moon, and Deb and I went out on the deck to watch it rise.  We also brought out some binoculars, and made a good scan of the whole of Leo, something I had not yet done.  I usually focus on one small area at a time, and am prone to lose "the big picture" as a result. 

     On Friday night we had about 45 minutes of dark sky before moonrise.  We set up our 2nd scope, the 4 1/4" Edmund Astroscan rft.  Sadly the main mirror has deteriorated to the point where we will have to send it off to Edmund Scientific to be replaced.  They will put in a new mirror and collimate it for around $140.  We recently purchased a tripod for it, as well as a red dot finder-scope.  One of the first things we looked at on Friday was M44, the Beehive Cluster.  Too large to fit into the field of most telescopes, the Astroscan was made for just such a task.  With the 28 mm eyepiece giving 16x, the cluster was quite impressive even in twilight.  Next, we scooted around some of the brighter stars and doubles in Leo, easily splitting Gamma at 50x (18 mm eyepiece with 2x barlow).  Gamma is one of the finest doubles out there, mag. 2.6 and 3.8, separated by 4" of arc, with both stars appearing golden yellow.  In the 12" it looks like a pair of headlights approaching, but it is still lovely in the 4".

     Last night, with about 90 minutes of dark sky before moonrise, we set up both scopes.  The evening had plenty of hazy clouds.  They went away for awhile, but then returned.  Despite this I was able to officially log M66 and eg 3628.  I have observed the Leo Triplet nearly every clear night for the past month and a half, and I have yet to tire of any of the three objects.  Last night I was able to use 200x on M66 and M65, getting bright, crisp views whenever the haze would move on.  It was easy to hop back and forth, even at high power.  This remarkable pair of galaxies was not noticed by Messier when a comet passed through the field in 1773.  According to Mechain, who did log them, the comet was probably too bright.  Imagine a comet passing through this area that blotted out those two bright galaxies!

     Noting the differences between the two Messier objects makes for good observational training.  M65 is more elongated, not quite as bright, and has a barely visible (in the 12") dark lane down its east edge.  This is more an impression than an easily observable feature, but I have seen it more than once.  M66 is the brighter galaxy, slightly less elongated, and has a blazing core that lies not in the center, but just a bit to the north.  This galaxy will take any magnification and still appear bright.  They both fit into my 100x field, and I will continue returning to them throughout the season.

     NGC eg 3628 is probably, after M31, one of the largest galaxies I have ever seen.  It is viewed edge-on, and is extremely elongated.  Using averted vision and 100x or 120x, it just goes on and on and on.  Almost featureless in the 12", other than more brightening near the middle, it still makes a wonderful site.  The darker the sky, the better this one appears, but even through haze I was able to get decent views.  NB: In March 2014 I easily observed the dark lane running all across this galaxy.  It was a superior observing site and a very good sky.

     Two other smaller galaxies appear near the triplet, and one of them is very much worth seeking out.  Immediately preceding M65 and M66 are three brighter stars in a straight N/S line.  Star 73 is the one in the north, with two slightly fainter ones due south.  Eg 3593 immediately precedes the middle star, and should be easily visible in an 8" scope.  It is elongated E/W, and pops into view more readily than eg 3628.  It is about 1/3 the size of that galaxy, but is a very enjoyable sight in the 12", its bright core easily seen.  With averted vision and 100x, the full extant of the arms can be seen.  If I cannot see this galaxy on a given night, then I know the sky is a bad one.  Lately it is my first test for a quality galaxy sky. 

     A fifth galaxy is also nearby, and makes an excellent final test for good skies.  Eg 3596 is the faintest of the five, lying north of the three stars just used to find eg 3693.  It is south of Theta, also called star 70.  This, too, is a big galaxy, oval but much harder to see than the others.  If this one pops up right away at low power, I know I have an excellent night of galaxy hunting ahead.  Last night it only appeared as a threshold object at medium-high powers.

     I have yet to officially log these fourth and fifth galaxies, though I have sketched eg 3693.  They will both be logged on the next good night.  All five galaxies are an easy star hop from one another, and I now know my way around this area extremely well.  If you have not visited these galaxies yet, I can highly recommend them.  Telescopes of 8" or higher will offer rewarding views, especially if you go back often.  In the 12", even from suburban skies, they are quite stunning and unforgettable.

Mapman Mike

Full Moon: Dark Skies Just Ahead

     The time just before and after full moon is perfect for tweaking one's observing plans.  Spring constellations are available to us for such a short period of time compared to summer, autumn and winter ones that careful preparation is even more important than usual.  I have been trying to make a decent start on Leo, and beginning two nights after full moon I hope to resume my work.  Immediate observing projects are to observe and sketch M 66 and eg 3628.  As the moonrise is gradually set back far enough in the evening, I will leave my back deck and set up my scope farther afield in dark sky locations.  I don't know yet whether I'll be able to observe in the 'preceding' area of Leo, where I have a whole collection of faint objects remaining to see, or if I will have to immediately move my observing session more towards the middle and 'following' sections of Leo.  Leo begins at about 9h 22m r.a., and continues until 11h 58m r.a.  No doubt I will still get lots done in Leo if it's clear, but not necessarily from the first pages of my object list, which generally follows r.a. of the constellation I am observing.

     One thing is for certain; Leo will set relatively early during the night.  Though I have notes prepared for Lyra, I decided I needed something to bridge the gap between Leo and Lyra.  Bootes seems to fit the bill nicely, though I have already observed it in some detail with the 8" scope.  Bootes begins at 13h 16m r.a., continuing to 15h 12m r.a.  Bootes is a galaxy-filled constellation of difficult NGC objects, and it contains not a single Messier object or galaxy of real brightness.  Besides galaxies, there is a lone, very faint globular cluster.  Having already viewed and sketched the brightest galaxies and the cluster, there may be little remaining for me to see except the dozens of much fainter galaxies.  While I don't mind reviewing previous brighter galaxies in the newer 12", I also want to add new NGC objects to my life list.  The good news is that right about now where I live, the trees usually begin to leaf.  When this happens, a lot of ground light pollution is blocked and the sky grows a bit darker.  Any slight advantage might make the difference between seeing a faint galaxy or not seeing it.  This year in southern Canada, however, we seem considerably behind in seasonal changes, and I may have to wait one more full moon before the trees are of much help.

     Leo also offers two close-up charts in Uranometria.  Charts A10 and A11 are galaxy-filled playgrounds, and I hope to make a good start on Abell 1367 (Chart A11).  I haven't yet decided on an observing strategy for this remarkable area.  I will first determine which objects and how many are actually available to me by having a quick look there.  If many or most of them are visible, then I will likely enjoy a galaxy-filled observing orgy over several nights.  As I enjoy star hopping so much, I'm certain to love galaxy hopping, too!  If my skies do a poor job of allowing me decent access, then I will likely plan a road trip with my telescope for next spring to somewhere very dark in order to experience this feast properly.  In fact, an upcoming post will likely be about dark site road trips.  Where to go, when to go, why to go and which way to go.  So stay tuned.

     Full moon is also a perfect time to tune up the scope and accessories.  Cleaning eyepieces and the finder-scope is a great idea, and perhaps doing some collimating on the secondary and primary mirrors isn't such a bad idea, either.  And of course it is a perfect time to scour the web and catch up on some blog reading!  Until next time enjoy the full moon, and join me in anticipating the dark-sky nights that will come soon afterwards.

Mapman Mike

Monthly Summary 1 (mid-March/mid-April 2013)

     With the moon now waxing, and the ten-day weather forecast predicting some form of rain every day for the foreseeable future, it is safe to say that dark sky observations have ended until after full moon on the 25th of this month.  I desperately tried to observe a few objects last night in Leo, but consistent clouds and haze made decent views impossible.  It is now time to summarize achievements during the past lunar cycle.  Despite many overcast nights, there were some remarkable successes since March 15th.  I got outside with the scope 8 times, and a few of those nights were near-perfect skies.  Many, however, ended early with incoming clouds.  Even worse was having clear skies predicted, staying up late only to find no such clear skies appearing.

     Despite some bad luck with weather a total of 19 new NGC objects were officially logged, many of them sketched as well as reported on with good old fashioned words.  One of the objects accounted for 4 of the new NGCs.  The Rosette Nebula in Monoceros has the following designations:  2237, 2238, 2239 and 2246.  The cluster itself, seen last lunar cycle, is 2244.  The nebula is vast and completely encircles the open cluster.  I could see nothing at all without a Skyglow filter, but with it and a low power eyepiece (28 mm) the emission nebula appeared as so much faint cloud interspersed among the rich stellar background.  So score 4 NGC right there!  I had hoped to also have a look at it with my Edmund 4 1/8" rft, but did not have the opportunity (more about this little scope soon).

     So besides the 4 galactic nebulae, I also viewed in detail this past month 5 open clusters, 9 galaxies and 1 planetary nebula.  One of those galaxies was M 65, and though I observed the entire Leo Triplet several times, M 65 was the only one so far to be officially entered into the logbook.  Sketches and verbal descriptions of M 66 and eg 3628 await better skies.  The Leo Triplet was easily the highlight of the observing month, with all three galaxies easily fitting into my 2" eyepiece at 43x, and just barely into my 1 1/4" 25 mm 60x eyepiece.  I now know that area so well that I can close my eyes in bed at night and still see it all clearly.  Two other worthy NGC galaxies lay within an easy star hop of the Triplet and were also seen on a few occasions, though not yet officially reported.  This is one of the great advantages of taking one's time when exploring the deep sky.  Once you have really explored and star hopped through an area over several nights, it will stay in your visual memory for a very long time.

     The Leo Triplet wasn't the only galaxy triplet observed this month.  NGCs 2872, 2873 and 2874, though much fainter and smaller, mark another worthwhile goal for 12" scopes or larger.  On my first attempt, only 72 and 74 were viewed, virtually touching.  72 is brighter than 74, though 74 extends further than its bright counterpart.  On a subsequent night I was able to see the third and very faint member, 2873, and it remains the faintest galaxy yet seen with the new scope.  And finally for Leo galaxies, the duo 2911 and tiny 2914 also make a worthy pair.  A nearby third member (2919) has yet to be found.  All three are an easy star hop from 6 Leo, a colourful double star.

     Monoceros is rich in clusters, though this month there were no real standouts.  oc 2353 was the best of the new ones, though I also liked 2252 (it looks like a Star Trek symbol to me) and 2364.  This last one is interesting because very little is said about it, and some photos show nothing at the site.  I definitely saw a cluster, however, and exactly where Uranometria puts it.  It is very small, and consists of 5 "brighter" stars in a curving line, with a field of very faint stars mixed in.  At lower powers the surrounding field is rich with stars, though the cluster itself is relatively barren.

     Of the non-NGC objects, my favorite was oc Collinder 106, a really huge affair that made for grand, informal sweeping.  Dense knots of stars can be found amidst its very bright and scattered field.  Two double stars also stood out this month.  8 Monoceros and 6 Leo are worth a stop if you appreciate doubles, and can easily be split in any modest telescope.  Other objects of interest are near each.

     Overall, I would have to say I was somewhat disappointed in how little I was able to accomplish in Leo.  Of the 9 galaxies officially logged, 8 of them are pretty faint, and a few are very faint.  They usually require some time to locate, see and reconfirm.   Early in the season I had hoped to complete about 5 pages from my extensive 32-page object list of the constellation this year.  I have yet to fully complete page 1!  With spring galaxy season nearly half over for Leo lovers, it will have to be very clear in May if I hope to reach my goal.

     With a little vacation approaching, I will be taking some time off from observing and blogging.  I will be back around the 1st of May, hopefully faced with 10-12 days in a row of clear skies.  May you have the same.

Mapman Mike

More About Galaxies

     I said awhile back that 5 of every 6 non-stellar objects plotted in Uranometria 2000 are galaxies.  That only includes objects to 15th mag.  If we dip down to 17th or 18th mag, virtually every object past 15 is a galaxy.  They are difficult to avoid if observing faint objects.  Since this blog is currently concerned with the NGC catalogue (and occasionally the IC list), I will only discuss the main list at this time.  With over 7800 objects of all types in the NGC list, galaxies still reign numerically supreme.  It might be of interest to look at which constellations have the most NGC objects within their boundaries, and just what type those objects are.  Because I live and mostly observe at latitude 42 degrees north, I will only discuss those constellations which are visible from mid-northern latitudes.

     The constellation (north or south) with the most NGC objects is........Virgo!  Not a huge surprise to seasoned observers, I'm sure.  Virgo has 637 NGC objects.  And guess what?  636 of them are galaxies!  There is one lone globular cluster (gc 5634).

     Number two on the list with the most NGC objects is....Ursa Major.  There are 407 NGC objects.  Only two are non-galaxies!  There is a single very famous planetary nebula and one open cluster.

     Number three constellation is Cetus.  Some of it is a bit low in the sky for me, but it is all there.  Cetus has 383 objects.  There is one lonely and very low surface brightness planetary nebula (NGC 246).  The rest are galaxies.

     Number four on the list and close behind is Leo, with 378 NGC objects.   Every single one is a galaxy!  No relief here, though it is peppered with some lovely double stars and multiples.  I am currently beginning my extensive and hopefully exhaustive exploration of this early spring constellation.  It will take me many years.  To date, I have located 13 of its NGC galaxies, though I've officially logged only 9 so far (it`s been pretty cloudy).

     Number five is Eridanus, a constellation that winds from north to south, meaning that I cannot see all of it from my latitude.  With 315 NGC objects, it has one reflection nebula and one planetary nebula.  All the rest are galaxies.

     So, then, the top five constellations for northern latitude viewers contain a total of 2,120 NGC objects.  That`s about 2/7ths of the entire list.  And a whopping 6 of those objects are non-galaxies!  Let`s continue through the top ten NGC constellations.

Number six is Pegasus.  With 298 NGC objects, only 3 are non-galaxies.

Number seven is Coma Berenices.  293 objects.  It has 3 globulars.

Number eight is Draco.  287 objects.  2 planetary nebula.

Number nine is Pisces.  270 objects.  All galaxies.

Number ten is Bootes.  267 objects.  1 globular.

     We are now up to 3,535 objects, nearly half of the NGC list!  All are galaxies except for 15 objects!  I don't know about you folks, but I find this quite astonishing and somewhat amusing.  "Well," you say, "what about those rich milky way summer constellations?"  OK.  Let's look at Scorpius.  Lots of interesting objects there.  Scorpius has a grand total of 71 NGC objects.  There are some totally amazing ones, too.  However, there just isn't a whole lot of them compared to those galaxy constellations (Sagittarius has 77 NGC objects).

     After the top ten NGC constellations comes Hydra, Canes Venatici, Hercules, Andromeda, Aquarius, Cancer and Lynx.  All are very heavy with galaxies.  I am not trying to prove any point here, but merely stating some interesting (for me) facts.  And no, I did not count the objects myself from the atlas.  This website does it for me.  
http://www.nightskyatlas.com/constellations.jsp

I did, however, scan through each constellation's list to search for non-galaxies, so there is some original research involved.

_________________________________________________________________________________

Here are a couple of older sketches each depicting a galaxy I saw with my previous scope, the amazing Edmund 8":

My first attempt to scan some early sketches.

eg 4565, Coma Berenices.  112x.

15'.8 x 2'.1  Vis. Mag. 9.5.  Sur. Br. 13.2.

One of the showpieces of the heavens.

eg 4448, Coma Berenices.  72x.

3'.9 x 1'.4  Vis. Mag. 11.2.  Sur. Br. 12.9

The star field is at least as interesting

as the galaxy.  The scale for this sketch

is obviously not the same as for the one

above--I cropped this one a lot.

Happy galaxy hunting!

 

Mapman Mike





Visual Magnitude versus Surface Brightness

     Any discussion about observing galaxies must inevitably come round to the subject of the galaxy's brightness or lack of it in the eyepiece.  Galaxies that I could barely see in my previous 8" scope are now much easier to locate, identify and discuss using my 12" mirror.  However, an entire new spectrum of much fainter galaxies is now available, going well beyond what the 8" might have seen.  If I suddenly started using a 16" scope, then the faintest ones now seen with the 12" would appear brighter, and a whole slew of new and fainter galaxies would be available to challenge my view.  This process would literally go on and on with each larger mirror.  There is no end to the faintness of distant galaxies, as evidenced by Hubble's deep field explorations.

     I am still trying to determine the faintest galaxy that I can view in my nearby dark sky with the 12" scope.  So far it has to be NGC 2873 in Leo, with a visual magnitude of 15.4 and a surface brightness of mag. 13.6.  While there are several fine explanations on the web as to exactly what visual mag. is, and surface brightness, I will give my own version here without equations, based on my current understanding and experience.

     Visual magnitude refers to how much actual light is coming from the galaxy to the observer's eye.  How it reaches the eye is greatly affected by the object's size.  Some bright galaxies (Messier 66, for example) have a bright visual magnitude, making them seem relatively easy to see in a wide range of small telescopes.  The visual mag. for M 66 is given as 8.9.  If that object was a star, it would be considered somewhat faint but still easily observable in a small telescope.  NGC 2873, by comparison, has a visual mag. of 15.4, making it nearly impossible to see if it was a star, except with a moderately large scope.  If 2873 was as large an object in the eyepiece as M66, it would never be seen in amateur scopes.  And yet the surface brightness levels of the two galaxies are not that far apart.  For M66 it is given as mag. 12.7, and for 2873 it is mag. 13.6.  There is less than a magnitude difference between these two vastly differing objects!  And yet in fact there is more than six magnitudes of difference between them in actual visual light.  A difference of one magnitude is 2 1/2 times, with mag. 10 being 2 1/2 times fainter than mag. 9, for example.  This is most interesting.

     The size of a galaxy, then, is important in determining its brightness, and in making it easier for the eye to see it.  Without getting mathematical (not my strength), let us take 3 hypothetical galaxies as our examples.  Our first galaxy is going to be sized at 1'.1 x 1'.0 (arc minutes).  This is a somewhat small object, and virtually round.  If the visual mag, was, say, 13 (from all the light coming from it), then the surface brightness would be the same mag. as the visual one.  That exact size of object has the same visual mag. as its surface brightness. 

     However, if we now expand the galaxy to 2'.2 x 2'.0, then the surface brightness decreases (there is an easy formula for this).  The same amount of visual light is now spread over an area 4x as large.  A galaxy of mag 13 might now become one with a surface brightness of 14.7 (not an exact answer, just an example, but it will be 4x fainter). 

     If we now shrink the galaxy to something like 0'.55 x 0'.5, then the same amount of light now arrives in a more compact, star-like package.  The surface brightness now increases, so that our imaginary galaxy with a visual mag. of 13 now seems more like a 12 mag. galaxy (again, just a rough answer--the formula is available on-line if you want exact answers).

     The upshot of all this is that a large galaxy that looks bright on paper might actually be very hard to see at the eyepiece, because its light is spread out over a large area (NGC 45 in Cetus is a good example--that one also has a bright star attached that interferes with seeing the fainter haze of the galaxy)).  And a tiny galaxy like 2873  might seem at first to be impossible to see, but is actually a bit easier because of its very small size (its actual size is 0'.8 x 0'.2).  Which magnitude is the one that observers should pay attention to, visual or surface brightness?

     In my experience, neither one should be used apart from the other.  Even taken together, there are still so many other factors to consider when hunting galaxies.  Some of these factors include how high above the horizon it lies, if it is near a bright star, the transparency of the sky and overall seeing conditions, and even how tired you are.  And if the galaxy is the same brightness as the sky background, it will be invisible.  When galaxies get too far west I stop observing them, as that area of sky is very light polluted.  I take both figures with me outside on the clipboard, along with the size.  If the galaxy is very large and bright, then the surface brightness formula only works to a certain degree.  A combination of the two magnitudes is often a better way to go.  M66 lists a visual mag. of 8.9 and a surface brightness of mag. 12.7.  You can't see a 12.7 mag. galaxy in a 4" telescope, but you can see M66.  Halfway between 8.9 and 12.7 is magnitude 10.8, which seems closer to the truth in this case.  A 4" scope can now work very hard and show the galaxy pretty well on a decent night.  My 'split the difference' method is unscientific, but seems to work for me in the field.

M66--is it really only 0.9 magnitude brighter than

 NGC 2873?  M66's vast dimensions (9'.1 x 4'.1) makes

its bright magnitude appear dimmer to the eye.

Both photos from

http://www.astrosurf.com/benoit/ngc.html

NGC 2872 on right.  NGC 2874 on left.  Both are easy

to locate in a 12" scope.  Much trickier is tiny NGC 2873,

lying just north of the two larger Leo galaxies,

 in the upper center of the photograph.  The photos

show true relative size of all galaxies depicted, including M 66, above. 

     The same goes for NGC 2873.  I could never hope to see a galaxy of 15.4 magnitude in my skies with a 12" scope, and the galaxy certainly doesn't reach its given surface brightness mag of 13.6 either.  Halfway between the two figures lies mag. 14.5, which gives a more reasonable ballpark estimate as to what my observing companion and I observed a few nights back.

     So for now, I am assuming that I can see a tiny mag. 14.5 galaxy in a good sky with my scope.  This will aid me in knowing which faint galaxies to attempt and which ones to pass up.
Of course the companion volume to Uranometria 2000 is also an awesome source of this information.

As ever, I am curious to hear what you think.
Mapman Mike

Leo Galaxy Hunt

     Shhh.  Be vewy vewy quiet.  I'm hunting gawaxies. Hehhehehehehe.

     The hunt is on, and my success rate is impressive, if a bit behind schedule.  Normally, my object list to-do pages are set up so as to take a full night's session per page (about a dozen or so objects over about three hours).  However, I have been on my 1st page of Leo for several nights now.  That's okay, as I am not hurrying through the universe, but taking my time and getting to know an obscure corner of the constellation.  10 NGC galaxies are listed on the first page of my goals for southeast Leo (32 pages in all for the constellation!).  Nearby stars include 2, 3, 5 and 6 Leo.  Five galaxies were observed on previous good nights without much trouble.  Three of the fainter ones fell victim to my 12" mirror last night, and now only two remain.

     I have enjoyed 4 nights in a row of clear skies in Essex County, Ontario, Canada, an almost unprecedented event, especially this time of year.  Because I have moved the scope to a site south of my nearest city, nearly up against Lake Erie, the skies are dark to the south, east, and overhead, thus making Leo a perfect area for observing.  However, Monoceros is hanging in there for some final observing early in the evening, allowing me to capture a few NGC clusters before heading into galaxy land (I can recommend oc 2253 for almost any aperture).  I am still involved with star clusters that surround 2244 and the Rosette Nebula.  This is one of the richest areas for sweeping into incredible star fields that the sky has to offer.

     In my 4 nights in a row of April observing, I have managed to log 14 new NGC objects!  I've also seen other non-NGC objects, mostly clusters in Monoceros, as well as several double stars and variables in both constellations.  While now convinced that my scope can find and resolve virtually any open star cluster listed in Uranometria, finding some of those fainter Leo galaxies has proven to be a more difficult project.  The last four nights have taught me much.  I still believe that I can find every single NGC galaxy in Leo, but I now realize how difficult and lengthy such a project will be, and how little of the faintest galaxies there is to see (basically the shape).  Still, it is fun hunting them down, and extremely rewarding when another one is captured in all of its faint, averted vision glory.  I could never locate them all from my back deck, which is much too suburban a location.  But just 12 minutes drive south of here, past the town where I live, is a whole new sky, much darker and friendlier to galaxy hunters.  We require the darkest skies possible.  And sometimes even that isn't enough.  Low humidity is also required.

     Some of the galaxies I found last night were among the faintest objects of the entire NGC catalogue.  Luckily I had an astronomer/friend with me to confirm sighting of one of the rarest for a 12".  NGC 2873 has the following specs:  0'.8 X  0'.2---visual mag. 15.4; surface brightness 13.1.  This is not a galaxy for the faint of heart, or for those quitters who don't see it on the first try.  What makes it worthwhile is that it is nestled between two other galaxies, and found immediately north of them.  2872 is pretty bright for a 12" scope, and probably even visible with a 10" under good skies.  Virtually touching it is 2874, though in the 12" at moderate power (150x) there is a tiny amount of black sky in between them.  This galaxy is much fainter, though significantly larger and very elongated.  With averted vision its dimensions go scooting quite far south and a bit north.  Then comes 2873.  Because of its tiny size, its surface brightness is just enough to make it visible to patient viewers with 12" scopes using averted vision (in a good sky).  It appeared to me, however briefly and faintly, as a small oval between the two bigger galaxies, but just to the north, and just south of a threshold star.  All three NGC objects fit easily into the 150x field of view.

     After seeing three faint galaxies in the same high power field, it was refreshing to view the Leo Triplet again, just barely fitting into my 25 mm eyepiece at 60x.  Sunglasses are now almost required by comparison.  This is another area of good galaxy hunting, but for now I just come to look in awe.

     I still have two faint galaxies to locate to conclude my first page of Leo.  I had predicted that my study of the entire constellation would require about 32 nights to cover the 32 pages of planned objects.  But I have now spent parts of five nights just on the first page!  So I have learned a lot about my scope and my skies, and will readjust my expectations accordingly.  With 85% success rate so far in Leo (and about 98% in Monoceros), I will continue my search for Leo galaxies and the darkest skies possible.  Please let me know if you are in the area of Leo or Monoceros (or Essex County, Canada), and how you are doing.

Mapman Mike

#10 Mirror Size

     I mentioned somewhere in an earlier post that if I had easy access to a truly dark sky, I would not require anything larger than an 8" telescope.  To any readers fortunate enough to have that dark sky on demand, along with an 8" scope, you have an ideal situation.  Or not.  It depends on what you are searching for, and how much you hope to see.  You won't be resolving any galaxies into millions of stars with it (nor with any other instrument).  A 6" scope would be quite nice in a great sky if an observer was after only the best and brightest of deep sky objects.  An 8" would be a big bonus for such a project.  For someone enamoured with the whole NGC list, however, a 12" scope in that beautiful dark sky would be darn near perfect.  A 14" objective would be a bonus. 

     I've owned a 3" reflector, a 4.5" reflector, an 8" reflector, and my current 12" Dob reflector.  Going from a 3" reflector to a 12" is not a bad upgrade.  One might think that going from a 3" to a 6" would double the light, and then double it again from a 6" to a 12".  Thus 4x the light gathering power belongs to the owner of a 12" compared to his neighbour with a 3" (refractor or reflector, makes no difference when merely gathering light).  However, this is not the case.

     In actual fact, even though my math is not exact to seventeen decimal points, upgrading to a 6" mirror from a 3" is already an increase of 4x the light-gathering power, not 2x.  7.1" sq. versus 28.3" sq. is 4x the light-gathering power.  Going from a 6" to a 12" increases it again by 4x, from 28.3" sq. to 113" sq. (pardon my non-metric calculations).  In my lifetime, I have increased my light gathering power by a whopping 16x.   I'm still not going to resolve M31 into individual stars with it, but the galaxy sure looks a lot brighter (and I can now see a few globular clusters in it!).

     When I observed with my 8" reflector, I had pre-cut cardboard circles on hand so that I could cover the top of the tube to see what certain objects looked like from a 4" objective and a 6" one.  With the holes cut away, it was also easy to actually see the difference between areas of different sized objectives.  I recently cut a new cardboard aperture to fit over the 12" tube, being 8" (off-centre).  That 8" hole now seems awfully small, with the huge amount of cardboard left over showing the full 12" circle.  Since upgrading from an 8" mirror to a 12", I have increased my light gathering power from roughly 50" sq. to 113" sq., or by about 125%.  It had not really struck me how much bigger that 12" mirror was until the cardboard cover was finished.

 A very rough 8" diameter hole cut from a 12" piece

of thick cardboard.  Black tape hides the bad cutting,
and keeps the circumference roughly even.  Not only
can I now see how objects compare at 8" and 12"

(roughly speaking), but I can really see how much

larger the 12" mirror is (more than 2x, or about 125%).

     We could push this discussion some more, discovering that a 16" mirror has about 201" sq., and a 22" one has around 383" sq.  These scope sizes and larger ones now regularly appear in amateur astronomers' inventories.  How long until we get one big enough to visually resolve Andromeda galaxy at a local star party?  Hmm, that requires around a 200" mirror.  Or maybe several 25" ones spread out and linked by computer on-site.  Maybe that day isn't really too far off after all.

Mapman Mike